Filtering Observables

This page shows operators you can use to filter and select items emitted by Observables.

• filter( ) — filter items emitted by an Observable
• takeLast( ) — only emit the last n items emitted by an Observable
• last( ) — emit only the last item emitted by an Observable
• lastOrDefault( ) — emit only the last item emitted by an Observable, or a default value if the source Observable is empty
• takeLastBuffer( ) — emit the last n items emitted by an Observable, as a single list item
• skip( ) — ignore the first n items emitted by an Observable
• skipLast( ) — ignore the last n items emitted by an Observable
• take( ) — emit only the first n items emitted by an Observable
• first( ) and takeFirst( ) — emit only the first item emitted by an Observable, or the first item that meets some condition
• firstOrDefault( ) — emit only the first item emitted by an Observable, or the first item that meets some condition, or a default value if the source Observable is empty
• elementAt( ) — emit item n emitted by the source Observable
• elementAtOrDefault( ) — emit item n emitted by the source Observable, or a default item if the source Observable emits fewer than n items
• sample( ) or throttleLast( ) — emit the most recent items emitted by an Observable within periodic time intervals
• throttleFirst( ) — emit the first items emitted by an Observable within periodic time intervals
• throttleWithTimeout( ) or debounce( ) — only emit an item from the source Observable after a particular timespan has passed without the Observable emitting any other items
• timeout( ) — emit items from a source Observable, but issue an exception if no item is emitted in a specified timespan
• distinct( ) — suppress duplicate items emitted by the source Observable
• distinctUntilChanged( ) — suppress duplicate consecutive items emitted by the source Observable
• ofType( ) — emit only those items from the source Observable that are of a particular class
• ignoreElements( ) — discard the items emitted by the source Observable and only pass through the error or completed notification